1. Field of the Invention
The present invention relates to a semiconductor device, wherein a semiconductor chip is mounted on the bed of a first frame, the tip end of each of the inner leads of a second frame is located above the semiconductor chip, and the bonding pads of the semiconductor chip and the inner leads of the second frame are connected together by bonding wires. The present invention also relates to a method for manufacturing this type of semiconductor device.
2. Description of the Related Art
Among well-known semiconductor devices, there is a type wherein a semiconductor chip is mounted on the bed of a first frame, the tip end of each of the inner leads of a second frame is located above the semiconductor chip, and the bonding pads of the semiconductor chip and the inner leads of the second frame are connected together by bonding wires. In this type of semiconductor device, the route extending from one inner lead of the second frame leading to the corresponding bonding pad is long. In the case where this route is long, water enters the interior of the semiconductor device since the route becomes a water route in most cases. Therefore, the above-mentioned type of semiconductor device is advantageous, in that a comparatively small-sized package, formed of sealing resin, can be employed for housing a large-sized chip.
However, the process for manufacturing the above semiconductor device is faced with the problems below.
When the inner leads of the second frame and their corresponding bonding pads are connected together by bonding wires, a passivation film formed on the surface of the semiconductor chip is likely to crack, due to the bonding force. Such a crack degrades the moisture-resisting of the semiconductor device. Moreover, if such a crack is deep, it may happen that semiconductor elements will be destroyed. Under these circumstances, conventional semiconductor devices of the above-mentioned type are not very reliable in operation, and the manufacturing yield of them is not very high.
To solve these problems, the inventor of the present invention considered coating the surface of the semiconductor chip with a shock-absorbing film. To achieve a sufficient shock-absorbing effect, however, the thickness of the film has to be more than a certain value. If the coated film is too thick, it contracts during the coating step. Since, in this case, the wafer coated with the film is subjected to physical stress, it may warp, resulting in damage to it.
The inventor also considered forming a shock-absorbing film on those portions of the second frame which face the semiconductor chip, so as to sufficiently absorb a shock. However, the interface between different materials is likely to become a water route along which water enters the interior of a resin-sealed semiconductor device. Therefore, if the shock-absorbing film is formed on the second frame, not only the interface between the molded resin and the second frame but also the interface between the molded resin and the shock-absorbing film may become a water route. Thus, water may easily enter the interior of a semiconductor device if this semiconductor device has a shock-absorbing film coated on the second frame.